D.C. officials have launched a formal investigation into why a fire department ambulance was not available to transport a police officer injured in a hit-and-run crash.

The Metropolitan Police Department said Wednesday that three arrests were made in the Tuesday evening crash, which left the eight-year department veteran with multiple injuries.

D.C. Council member Tommy Wells, who heads the council committee that oversees the police and fire departments, said he is seeking reports from both agencies on the incident and a deputy mayor confirmed an investigation is under way to determine why no ambulances were available to respond. An ambulance from neighboring Prince George's County was eventually dispatched to the scene and arrived about 20 minutes after the crash.

"They've got a timeline and now they are working to determine exact reason why an ambulance was not available," Mr. Wells, Ward 6 Democrat, said. "It could be ambulances were on other calls, could be not enough ambulances were in service. ... I'm obviously very upset about it."

The crash happened around 6:30 p.m. Tuesday at 46th and A streets in Southeast D.C. when the officer, who was on a motor scooter, was struck by a Lexus. Shortly after the crash, police stopped and arrested three Southeast D.C. men — the vehicle's driver, 24-year-old Kevin Burno, and two passengers 22-year-old Antonio Parks and 25-year-old Darrin Twisdale. Mr. Burno was charged with felony assault on a police officer and the two passengers were charged with possession of an open container and obstruction of justice.

A D.C. paramedic responded to the scene via fire engine and began providing aid to the officer within eight minutes of the call being placed, but none of the 39 ambulances on the street that night were available to transport the officer, Deputy Mayor for Public Safety and Justice Paul Quander said.

"We're looking to see why the units were not available for service. Some were at hospitals, some were on route, others we need to account for," Mr. Quander said. "We think we have enough resources that are in place but we want to make sure we are managing those resources as best we can."

The injuries the officer received to his lower extremities are not life-threatening, but officials said it will likely be a long road to recovery.

"He's facing a lot of surgeries down the road," Mr. Wells said.

Mr. Quander said he does not believe the officer was put in any greater "peril" because of the wait for an ambulance, which was first reported by the Washington Examiner.

It's not entirely uncommon for neighboring jurisdictions to provide "mutual aid" for one another, but Tuesday's incident, coupled with a New Year's Eve incident during which a D.C. man died from a heart attack after waiting 40 minutes for an ambulance, has highlighted what one union official calls a "system failure."

"We've got a real problem and it's just going to get worse," said Kenneth Lyons, president of the American Federation of Government Employees Local 3721, which represents the department's civilian paramedics. "You can't pass the buck on the individuals in the system anymore. This is a system failure."

Without more ambulances staffed with paramedics, the District is going to continue to run into service problems which will only get worse as call volumes increase in the spring and summer months, Mr. Lyons predicted.

"If we don't make changes ... this is going to get worse. This will pale in comparison," he said.